chore(autoware_behavior_velocity_stop_line_module): resolve warnings of clangd

[yhisaki]

Description

This PR is about refactoring.
Resolve clangd warnings.

Related links

How was this PR tested?

Tested on psim.

Notes for reviewers

None.

Interface changes

None.

Effects on system behavior

None.

[github-actions]

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[codecov]

Codecov Report

Attention: Patch coverage is 16.66667% with 5 lines in your changes missing coverage. Please review.

Project coverage is 29.27%. Comparing base (a7a75ea) to head (b82a13f).
Report is 16 commits behind head on main.

Files	Patch %	Lines
...e_behavior_velocity_stop_line_module/src/debug.cpp	0.00%	2 Missing ⚠️
...e_behavior_velocity_stop_line_module/src/scene.cpp	0.00%	2 Missing ⚠️
...behavior_velocity_stop_line_module/src/manager.cpp	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8382      +/-   ##
==========================================
- Coverage   29.28%   29.27%   -0.02%     
==========================================
  Files        1609     1614       +5     
  Lines      119424   119480      +56     
  Branches    51491    51495       +4     
==========================================
+ Hits        34979    34980       +1     
- Misses      75178    75233      +55     
  Partials     9267     9267              

Flag	Coverage Δ		*Carryforward flag
differential	13.02% <16.66%> (?)
total	29.29% <ø> (+<0.01%)	⬆️	Carriedforward from a7a75ea

*This pull request uses carry forward flags. Click here to find out more.

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